Some of known kneader/stirrers for kneading and stirring powder liquids and high-viscosity fluids are used as polymerizers for increasing the degree of polymerization of a polycondensation resin with a low degree of polymerization which has been supplied into the kneader/stirrer as a material to be processed, by stirring the resin supplied (see e.g. JP Patent 4112908 and JP Utility Model Publication 62-123238U).
The kneader/stirrer (polymerizer) disclosed in JP Patent 4112908 includes a tubular casing defining therein a processing chamber, and a large number of plate-shaped impellers mounted in the processing chamber so as to be arranged in the axial direction and configured to stir a polycondensation resin. The impellers have lightening holes. The lightening holes enhance polymerization reactions and evaporation of e.g. solvents because the resin is formed into films in the lightening holes.
The device shown in JP Utility Model Publication 62-123238U includes two rotary shafts extending parallel to each other in the processing chamber, a large number of first disk-shaped impellers mounted to one of the rotary shafts so as to be arranged in the axial direction, and second disk-shaped impellers mounted to the other rotary shaft at the same axial positions as the respective first impellers. The respective impellers are fixed to the respective rotary shafts at points offset from the centers of the respective impellers in a predetermined direction by a predetermined distance such that when the two rotary shafts are rotated in the same direction at the same speed, each pair of first and second impellers at the same axial position are eccentrically pivoted while kept in contact with or in close proximity to each other, whereby resin adhered to each of the pair of impellers is removed by the other impeller, while resin adhered to the inner wall of the processing chamber can be also removed by the impellers. This device thus has a self-cleaning ability.
The kneader/stirrer (polymerizer) disclosed in JP Patent 4112908 has a problem in that resin tends to be strongly adhered to the outer peripheries of the impeller and the inner wall of the processing chamber, so that solidified resin tends to become wedged between adjacent impellers or between an impeller and the inner wall of the processing chamber, thus causing trouble during operation.
On the other hand, with the device disclosed in JP Utility Model Publication 62-123238U, due to its self-cleaning ability, resin stuck on the outer peripheries of the impellers and the inner wall of the processing chamber can be removed to a certain extent. But since the impellers are disk-shaped members, they cannot sufficiently remove resin stuck on the impellers and the inner wall of the processing chamber. Rather, such impellers could press resin against the opposed impellers and against the inner wall of the processing chamber, thus causing resin to be more strongly adhered to the impellers and the inner wall of the processing chamber. Thus this device is also not free of the problem resulting from solidified resin becoming wedged between parts.